Minor markup tweaks (Sy instead of Nm).

@@ -233,11 +233,11 @@
 .Xr nroff 1
 and
 .Xr troff 1 ,
 the use of multi-byte characters may not be supported.
 .Sh INTERFACE STABILITY
-.Nm Obsolete Committed .
+.Sy Obsolete Committed .
 The
 .Xr mdoc 5
 package should be used instead.
 .Sh SEE ALSO
 .Xr eqn 1 ,